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  <title>Document</title>
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<body>
  <script>
    //函数表达式
    let average = function (Chinese, English, Math) {
      let sum = Chinese + English + Math;
      return sum / 3;
    };

    //简写形式1：函数体只有返回值语句
    let average = function (a, b, c) {
      return (a + b + c) / 3;
    };

    //简写形式2：只有一个参数，圆括号可选
    let fn = function (v) {
      return v;
    };

    //简写形式3：没有参数时，圆括号不可省略
    let fn = function () {
      return 123;
    };
  </script>
</body>

</html>